2. Histopathology and radiology Flashcards
What are the 2 broad categorisations of mature bone?
Cortical
Cancellous
What % of bone is cortical and where is cortical bone most abundant?
80% of bone
Long bones
Describe the structure of cortical bone
Mature, lamellar bone - PARALLEL lamellae
Describe the structure of cancellous bone
Mature, lamellar bone - CONCENTRIC lamellae
What is the primary function of cancellous bone and where is it most abundant?
Metabolic fx - can dissolve/ resorb quickly for Ca++ homeostasis
Vertebrae and pelvis
Describe the process of mineralisation
Process through which an organic substance becomes impregnated by inorganic substances
What name is given to immature bone? Describe it structure
Woven bone
Irregularly-arranged collagen
What are the cannaliculae in bone?
Communication channels for osteocytes
What can be seen where there is osteoclast activity?
Howship’s lacunae
= “bite-marks” where breakdown is occuring
Recall the relative proportions of organic and inorganic matter in bone, and summarise the composition of each of these
Organic (cells and protein matrix) = 35%
Inorganic (Ca hydroxyapatite) = 65%
What is the role of the RANK ligand in bone homeostasis?
When RANK combines with RANK-L osteoclasts are stimulated to differentiate
By what mechanism is osteoclast action inhibited?
Osteoprotegerin
Inhibitor of RANK:RANK-L binding
Where are osteocytes located in bone?
Lacunae
Distinguish between primary and secondary osteoperosis
Primary = age-related, post-menopause Secondary = caused by drugs (eg thyroid drugs) or systemic disease
Recall the key distinguishing features of osteoperosis from other metabolic bone diseases
NORMAL mineralisation so serum biochemistry is normal - just a reduced mass of bone
What is raised ALP indicative of? Give 4 examples of where this might be seen
Increased bone turnover
- Paget’s
- Osteomalacia
- Bony Mets
- HyperPTHism
Sumamrise the possible radiological findings in osteoperosis
MAY BE NORMAL
OR
1. Osteopaenic
2. Osteosclerotic
Why might osteoperosis demonstrate osteopaenia
Loss of bone quantity rather than quality
How does osteopaenia appear radiologically?
Reduced opacity
What is osteosclerosis?
Increased bone density
Recall 2 key features of osteomalacia radiologically
- Looser’s zone fractures (horizontal fracture in cortical bone)
- Codfish vertebrae
(biconcave vertebrae)
Recall 2 radiological features of Paget’s disease
- Cortical thickening
2. Coarsening trabeculae
Describe how primary and secondary hyperPTHism can be distinguished radiologically?
Primary = bone resorption
Secondary = bone resorption AND INCREASED DENSITY
Bone resorption has appearance of erosion, and can lead to “brown tumour”
What is renal osteodystrophy?
Comprises all the skeletal changes of CKS - a combo of: OsteoMALACIA OsteoSCLEROSIS OsteoPEROSIS OsteoTITIS FIBROSIS CYSTICA
Describe the serum biochemistry of renal osteodystrophy (phosphate, calcium, PTH, pH)
HIGH phosphate
LOW calcium
HIGH PTH
Metabolic acidosis
How does sclerosis appear radiologically?
Rugged vertebrae (Jersey spine)
Recall 3 radiological features of renal osteodystrophy
Brown tumour
Jersey Spine
Soft tissue calcification around vessels
Recall 2 radiological features of Rickets
Cupped and frayed metaphysis due to increased stress
Widenened unmineralised growth plate
